MICROSTRUCTURE DEPENDENT MODELING FOR SPECIMENS MADE OF SINGLE-CRYSTAL SUPERALLOYS LOADED UNDER TORSION

Microscopic dislocation mechanisms were investigated by means of trans mission electron microscopy in specimens made of CMSX-4 loaded at 1000 degrees C. Torsional tests were carried out on tubular specimens. In order to model the anisotropic behaviour of single crystal superalloys , two cases are distinguished: At low temperatures, the gamma'-particl es remain cubic and the initial cubic symmetry of the continuum is pre served. The overall cubic symmetries of the component disappear during rafting of the gamma' phase, which occurs at low stresses and high te mperatures. Creep potentials adapted to the evolution of the microstru cture are presented. Predictions of the anisotropic creep behaviour ar e discussed. (C) 1997 Published by Elsevier Science B.V.